Clean Application

While the Quickstart focuses on running a sample that's located within the Zephyr file-hierarchy, it's simple enough to create a new application that's separate from Zephyr.

Prerequisites

goliothctl and west installed
Authenticated with Golioth - see Authentication
Have a project - see Create a Project
Have a provisioned device and credential for it - see Authorizing Devices
The golioth/zephyr codebase set up on your machine. See the Set up Zephyr page for the ESP32.
A toolchain installed. In this guide, the toolchain for the ESP32 will be used.

Setting up file structure

For reference, this is the file structure of the app we're going to set up:

example-app/
├── CMakeLists.txt
├── Kconfig
├── boards
│   └── esp32.conf
├── prj.conf
└── src
    └── main.c

To make this, create a new directory for your app (we called ours example-app). Feel free to name it whatever you'd like.

Inside this directory, create 3 files: CMakeLists.txt, Kconfig, and prj.conf.

Here are their contents:

CMakeLists.txt
cmake_minimum_required(VERSION 3.20.0)

find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
project(hello)

target_sources(app PRIVATE src/main.c)

Kconfig
mainmenu "Golioth application options"

if DNS_RESOLVER

config DNS_SERVER_IP_ADDRESSES
    default y

config DNS_SERVER1
    default "1.1.1.1"

endif # DNS_RESOLVER

source "Kconfig.zephyr"

prj.conf
CONFIG_GOLIOTH_SAMPLES_COMMON=y

# Generic networking options
CONFIG_NETWORKING=y
CONFIG_NET_IPV4=y
CONFIG_NET_IPV6=n

# Logging
CONFIG_NET_LOG=y

# Network Shell
CONFIG_NET_SHELL=y

# TLS configuration
CONFIG_MBEDTLS_ENABLE_HEAP=y
CONFIG_MBEDTLS_HEAP_SIZE=10240
CONFIG_MBEDTLS_SSL_MAX_CONTENT_LEN=2048

# Application
CONFIG_MAIN_STACK_SIZE=4096

CONFIG_GOLIOTH=y
CONFIG_GOLIOTH_SYSTEM_CLIENT=y

CONFIG_MINIMAL_LIBC_MALLOC_ARENA_SIZE=256

CONFIG_LOG_BACKEND_GOLIOTH=y
CONFIG_LOG_PROCESS_THREAD_STACK_SIZE=2048

CONFIG_GOLIOTH_SYSTEM_CLIENT_PSK_ID="<the PSK ID>"
CONFIG_GOLIOTH_SYSTEM_CLIENT_PSK="<the PSK>"

CONFIG_GOLIOTH_SAMPLE_WIFI_SSID="<WIFI SSD>"
CONFIG_GOLIOTH_SAMPLE_WIFI_PSK="<WIFI PASSWORD>"

As you can see at the end of prj.conf, there are some values that you'll need to fill in yourself that depend on your registered devices and environment.

Now create two directories, boards and src. Inside of boards/, create a configuration file for the board you're using. In this guide, we're using an ESP32.

note

For the most part, you can copy these configuration files from Zephyr and Golioth samples.

boards/esp32.conf
CONFIG_WIFI=y
CONFIG_HEAP_MEM_POOL_SIZE=98304

CONFIG_NET_L2_ETHERNET=y

CONFIG_NET_DHCPV4=y

CONFIG_MBEDTLS_ENTROPY_ENABLED=y
CONFIG_MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED=y
CONFIG_MBEDTLS_ECP_ALL_ENABLED=y

CONFIG_ESP32_WIFI_STA_AUTO_DHCPV4=y

CONFIG_NET_L2_WIFI_SHELL=y
CONFIG_GOLIOTH_SAMPLE_WIFI=y

An overlay file for the ESP32 is used to enable the Wi-Fi

boards/esp32.overlay
&wifi {
    status = "okay";
};

Create one file, main.c, inside src/.

For this example, the contents should be a simple logger.

src/main.c
/*
 * Copyright (c) 2021 Golioth, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(golioth_hello, LOG_LEVEL_DBG);

#include <net/golioth/system_client.h>
#include <samples/common/net_connect.h>
#include <zephyr/net/coap.h>

static struct golioth_client *client = GOLIOTH_SYSTEM_CLIENT_GET();

static K_SEM_DEFINE(connected, 0, 1);

static void golioth_on_connect(struct golioth_client *client)
{
    k_sem_give(&connected);
}

void main(void)
{
    int counter = 0;
    int err;

    LOG_DBG("Start Hello sample");

    if (IS_ENABLED(CONFIG_GOLIOTH_SAMPLES_COMMON)) {
        net_connect();
    }

    client->on_connect = golioth_on_connect;
    golioth_system_client_start();

    k_sem_take(&connected, K_FOREVER);

    while (true) {
        LOG_INF("Sending hello! %d", counter);

        err = golioth_send_hello(client);
        if (err) {
            LOG_WRN("Failed to send hello!");
        }
        ++counter;
        k_sleep(K_SECONDS(5));
    }
}

Building the Application

note

This guide is for the ESP32, so setting up the required toolchain for other boards will be slightly different.

Look at the Zephyr documentation for your particular board to learn more about setting up the toolchain.

Make sure that west can find the golioth/zephyr codebase on your local machine. You'll have to source a particular file to do so.

source ~/golioth-zephyr-workspace/zephyr/zephyr-env.sh

This will set the $ZEPHYR_BASE environment variable, as well as make sure west can find the correct subcommands.

note

The exact paths may not match up with what is shown here. Look at Set up Zephyr (on ESP32) page for more information about setting up the toolchain. environment variables.

Now, to build it:

west build -b esp32 -p

And to flash it to the board (exact paths may vary)

west flash --esp-device=/dev/cu.usbserial-14210

Results

If prj.conf is set up correctly (e.g. CONFIG_GOLIOTH_SYSTEM_CLIENT_PSK_ID, CONFIG_GOLIOTH_SYSTEM_CLIENT_PSK, CONFIG_GOLIOTH_SAMPLE_WIFI_SSID, and CONFIG_GOLIOTH_SAMPLE_WIFI_PSK are all correct), then will see the logs emitted by your device by running:

goliothctl logs --interval 10m

Prerequisites​

Setting up file structure​

Building the Application​

Results​

Prerequisites

Setting up file structure

Building the Application

Results